Chris Haston/NBC(LOS ANGELES) -- Good night, Jay Leno. On Thursday, the longtime host of The Tonight Show will end his 22-year run on the NBC program.

Leno's final guests will be Billy Crystal and Garth Brooks. Crystal will be on the show for sentimental reasons: he appeared on the debut night of The Tonight Show with Jay Leno.

Leno officially replaced the legendary Johnny Carson as Tonight Show host on May 25, 1992. He was famously awarded the job over NBC Late Night host David Letterman, who would soon become his CBS rival. The drama surrounding the network's succession plan for Carson inspired a best-selling book, The Late Shift, and a TV movie of the same name.

For many years, Leno entertained viewers with signature bits like "Headlines," in which he displayed and read headlines from around the country that typically contained grammatical or spelling mistakes, and "Jaywalking," in which Leno would conduct man-on-the-street interviews with pedestrians who were clueless about current events.

Over the years, Leno didn't earn a reputation as a hard-hitting interviewer, though his questioning of Hugh Grant in 1995 -- after the actor had been caught with a prostitute -- became legendary when he asked Grant, "What the hell were you thinking?"

Leno's show turned political at times, too. It was on The Tonight Show, in 2003, that actor Arnold Schwarzenegger announced he would enter the California gubernatorial race. He was elected later that year.

Leno also welcomed President Obama in 2009 for what was the first appearance by a sitting president on a late-night talk show.

Leno's monologues were heavy on political jokes, especially when President Bill Clinton was involved. A recent study by the Center for Media and Public Affairs at George Mason University determined that Clinton was a bigger target for Leno than any other political figure or celebrity. Leno told more than 4,600 jokes about Clinton in his 22 years as Tonight Show host.

Of course, Thursday won't mark the first time that the 63-year-old Leno has left The Tonight Show. In 2009, Late Night host Conan O'Brien took over the program after he was promised the gig five years earlier. Less than a year later, NBC had a change of heart, had a bitter split from O'Brien, and returned The Tonight Show to Leno in 2010.

O'Brien, who'd lasted only seven months on The Tonight Show, landed on his feet with a new show at TBS, where he remains today.

In recent weeks, Leno has been complimentary about his latest successor, Late Night host Jimmy Fallon, who makes his Tonight Show debut on Feb. 17. Another Saturday Night Live alum, Seth Meyers, will take over hosting duties for Late Night on Feb. 24.

TV Guide's Michael Schneider isn't so sure that Leno is ready to give up The Tonight Show again -- at least not yet. He tells ABC News Radio, "If [NBC] had told him, hey, we want you to stick around for another two years, he would have stuck around for another two years. But he was asked, and he did agree that he would go ahead and step aside for Jimmy Fallon. But all things being equal, I think Jay is kind of wishing he could stick around for a few more years."

So what's on tap for Leno? He may be open to doing another TV show, according to former Tonight Show producer Dave Berg.

"I think if an opportunity comes up to do a daily monologue show, topical material, say at CNN, I think he's going to take it. But we're not going to hear anything about it until his contract expires in September," Berg comments.

Wednesday night's next-to-last installment of the show featured The Voice coach and country music star Blake Shelton and Gravity Oscar nominee Sandra Bullock -- who got emotional speaking about what the outgoing host means to her.

"I'm gonna start crying," the teary Blind Side Oscar winner said before exhaling deeply to regain her composure. "You've always been so kind...When I made crazy life decisions, you never questioned...you were always just so welcoming and every single person on your crew was like that way consistently and I just felt special even when I felt very insecure. And everyone I think in this room and this country has felt that every day that you've been in their home."

For his part, Shelton said of the comedian, "I want to thank you for keeping the world on an even playing field on this show and never -- as a comedian -- never pushing your personal agendas or politics." The star then gifted Leno with a rack full of his typical casual outfit of a denim shirt and jeans.